1. Field of the Invention
The present invention relates to a method for controlling multiple machining processes on a machine tool, and in particular, to a method for controlling multiple machining processes on a die-sink erosion machine, and a device suitable for this purpose.
2. Description of Related Art
Such machine tools usually have a numerical control, e.g., an NC or CNC control. The control data required for the numerical control, such as position and/or path or contour data, as well as the parameter data of the desired workpiece machining, are transmitted to the control device in the form of control inputs and are converted there into control signals, e.g., for servo drives of the machine tool. An example of this is a spark erosion machine, specifically a die-sink erosion machine. Such die-sink erosion machines are used, among other things, for manufacturing molds with extremely high machining precision. A number of machining processes are hereby performed on one or more workpieces. Depending on the machining type, such as roughing or finishing, often different tool categories, i.e., different types of sinker electrodes, are used for performing these machining processes. If, in addition, the geometry or contour of the performed machining changes, the electrode of the die-sink erosion machine also must be changed in most cases. This means that depending on the number, versatility, and quality requirements of the machining processes to be performed in a modern die-sink erosion machine, the machining electrodes that are used must be changed several times during the total duration of the tool machining.
When setting up a die-sink erosion machine for such a complex machining, the machine operator must in the control device of the machine set the control inputs that determine which work steps of a machining job must be performed in which sequence with which machining electrode on which workpiece. Standard, state-of-the-art control processes of the initially mentioned type require control inputs in the form of closed xe2x80x9cprogramsxe2x80x9d, so-called sequential control programs, for this purpose. Such a control program defines all control data in respect to machining and machining electrode for each point in time during the overall machining. The control data that were obtained from the control inputs are defined in sequential order. When changing the machining tool, which happens very frequently with a die-sink erosion machine, the entire tool description must each time be repeated in its entirety in the control program and may have to be edited if different types of tools are used. With increasingly more complex overall machining, it becomes more and more time-consuming for the machine operator to create the control program and change it, if needed. In addition, for economical reasons machine standstills should be avoided if at all possible.
The state of the art indeed also includes methods for the so-called object-oriented programming of machine tools, for example from: Prof. Dr. Ing. Eversheim, Dipl.-Ing. Lenhart, Objektorientiert Programmieren, in: Industrie-Anzeiger 82/1991, p. 38-40. In contrast to sequential control programs, these methods use program components that can be reused over and over again for changing the control program. But in this context, an object-oriented structure of the source program is suggested, in which the technical and geometrical information of a workpiece to be produced and/or of the machine tool are categorized in different object classes. A reprogramming in this process presents a direct manipulation of the source program which, as a rule, can only be performed by a machine operator with special programming skills.
Similar methods are known from the following sources: STORR, A., HOFMEISTER, W.: Strukturen zur Programmierung von NC-Mehrschlittendrehmaschinen. In: wtxe2x80x94Produktion und Management 84, 1994, p. 26-30; BATZ, Thomas, et al.: Objektorientierte Modellierung von Produktionsprozessen. In: Informatik Forsch. Entw., 1995, p. 26-40; and PLANKEN, Bettina, et al.: Mit der richtigen Entwicklungsumgebung zum Erfolg. In: Elektronik, 25, 1994, p. 111-124. The previous explanations apply analogously to these methods.
The invention at hand attempts to improve machine tools, in particular die-sink erosion machines, with respect to their user-friendliness during setup and/or any reprogramming during the machining.
Accordingly, one aspect of the present invention creates a method for controlling a number of machining processes on a machine tool with the help of a control device that controls at least one tool for performing said number of machining processes under the direction of a control program, whereby the control program is created using a description of the tool(s) required for performing the machining processes, and whereby the data for describing the tool are hereby divided in the control device into: (a) abstract tool data for describing a standard tool (V1, V2); and (b) specific tool data for correcting and/or adapting the abstract tool data to the actually used tool (R1, R2) or to machine-specific characteristics, whereby the tool description in the control program is obtained by linking the abstract tool data with the specific tool data. For this purpose, the control device, for example, a CNC control, is provided with at least one data memory for the permanent storing the abstract tool data and the specific tool data as well as with a user interface for linking the abstract tool data with selected, specific tool data.
The abstract tool data already contain all essential information about the tool(s) required and planned for performing a specific (individual) machining job. Such a machining process (from hereon called a xe2x80x9cmachining jobxe2x80x9d) on a workpiece provides a specific, desired geometry or contour of the tool machining job, for example a specific die-sink contour of a die-sink erosion, in a specific machining quality, for example a specific machining quality, such as roughing, pre-smoothing or finishing, so that a machining job in most cases requires the use of several tools of different quality categories. This is therefore related to the description of standard or specified tools required for performing a specific, desired machining job, whereby this abstract description also contains all essential machining-specific information of the tools, for example the basic tool geometry, the basic tool shape, the tool material, the tool type, for example whether it is a roughing or a smoothing electrode of a die-sink erosion machine. The specific tool data then contain only the correction data, for example in respect to the exact dimensions of the actually used tool, such as the actual smaller than specified size, which may differ from the (assumed) smaller than specified size of the specified tool, as well as machine-specific data, such as, for example, the exact chucking position of the tool, the current position in a tool magazine for an automatic tool change or the current wear status of the actually used tool.
The basic idea of the invention is therefore to generalize the tool description, i.e., to abstract it independently from the actually encountered situation in the machine tool and the actual tools used in the description of a standard tool, so that the tool description can already be performed before the actual machining, outside the workshop. When setting up the machine tool, the machine operator is able to utilize an already existing abstract tool description and supplement it with only those control inputs related to the specific tool data, and in this way is able to set the entire tool description for the control device. These inputs permit an especially speedy programming of the machine tool at the work site, and ajust as speedy modification programming or reprogramming of complex machining sequences in which the abstract and specific data groups can be combined as desired and reused over and over again in the manner of data modules.
It is preferred that an intelligent data generator automatically determines the sequence of the technology and process parameters of individual work steps of a particular machining job on the basis of the abstract tool data together with the geometrical and machining contour data and technology and process parameter sets available in databases.
In a particularly preferred application of the control concept according to the invention in a die-sink erosion machine, several electrodes for performing a particular machining job are combined by an administration system of the control device into an electrode family. The data describing the electrode family are hereby divided in the control device into: (a1) family data applying to all electrodes of the electrode family, for example related to electrode material and basic electrode geometry; (a2) abstract electrode data (so-called data of virtual electrodes) that contain information about a standard electrode for performing a particular machining job; and (b) specific electrode data about the electrodes actually used for performing this machining job (so-called data of real electrodes).
The family data are superordinate to the abstract and specific electrode data; otherwise the abstract and specific electrode data correspond to the previously mentioned concept of the abstract and specific tool description. The overall description about an electrode or electrodes required for a specific machining job is obtained from the sum of the abstract and specific electrode data and the superordinate family data of the electrode family. By using the control""s user interface, a separate electrode can be specified for a number of different machining processes that again comprise several work cycles, each of which has several work steps, i.e., in that the electrode administration system of the control assigns several different real electrodes belonging to the same electrode family to, for example, a virtual electrode. It is preferred that different types of electrode families are provided for different machining jobs, i.e., for different die-sink contours or die-sink geometry, where, depending on the number of work cycles and/or work steps, said electrode families contain different electrodes that are defined by the combination of specific and abstract data.
In a preferred embodiment, the structure of the machine control of the die-sink erosion machine is object-oriented. It is preferred that hereby two object structures are provided. One object structure relates to performing the total of all machining processes, whereby the following objects that are hierarchically ranked in the following descending order are provided: the die-sink erosion machine as such, a tool table, a pallet or workpiece group, a workpiece, a machining job group, a machining job, a work cycle, and/or a work step. In addition to this machining object structure, the machine control comprises a tool object structure that relates to the tools required for all of the machining processes and has the following objects: an electrode family group, an electrode family and/or virtual electrode and a real electrode. When the program is created, the objects of the tool object structure are linked with selected objects of the machining object structure.
An xe2x80x9cobjectxe2x80x9d is defined as an organizational and functional unit of the die-sink erosion machine on which measures for completing the desired workpiece machining are performed by the control of the die-sink erosion machine. The division or assignment of control measures to such objects, for example to the electrode family group object that applies to all hierarchically subordinate objects permits the machine operator to directly set up the control of the die-sink erosion machine in the workshop, i.e., specify the measures to be performed on the object, without detailed knowledge of the source program.
In a further preferred embodiment of the tool description according to the invention, the abstract tool data, and in particular electrode data, also contain data about the life span of a tool, i.e., the maximum number of machining processes or work cycles of a particular machining for which a tool can be used. This information permits the preferred setup of an automatic tool administration or tool management system in the control of the die-sink erosion machine. Once a certain tool has performed the maximum permissible number of machining processes, it is automatically excluded by the administration system from further machining or is assigned to another machining type for which this tool can still be used. By using the tool description according to the invention, such a downgrading is achieved by linking the previous specific tool data with a set of new, abstract tool data that contain information for performing the downgraded machining type.
As a supplement to the tool administration according to the invention, the specific data preferably also contain information about the current wear status and/or maximum permissible wear of a particular tool. This information can be obtained in different ways. In the case of a die-sink erosion machine in which several machining jobs, each of which has several work steps that again are combined into work cycles, are performed consecutively, the maximum electrode wear is specified by the maximum number of work cycles or work steps that can be performed with an electrode by way of an electrode administration system that counts and registers the number of performed work cycles or work steps during the machining.